1. Field of the Invention
The present invention relates to a prober used for testing liquid crystal display (LCD) panels, organic EL panels, and other display panels, and a testing apparatus thereof.
2. Discussion of the Background Art
The wafer probers cited in JP (Kokai) 6-53297 and JP (Kokai) 7-84003 are known for improving measurement accuracy and speed of wafer probers that are used to test semiconductor wafers. It is necessary to apply a voltage or a potential to the semiconductor substrate and by means of these wafer probers, voltage can be applied to the chuck. This potential is not limited to ground potential, and FIG. 2 of JP (Kokai) 7-84003 cites technology whereby an active guard is used as a countermeasure to noise in order to shield at guard potential. Moreover, technology whereby a region that includes the chuck and the device under test is enclosed by a conductor as an EMI shield is shown in FIG. 3 of JP (Kokai) 6-53297.
However, silicon is grown on the glass insulator of the display panel and the display panel theoretically takes on an SOI (Silicon-on-Insulator) structure. Therefore, it is not necessary to apply potential to the glass insulator with probers for display panels that are used for testing liquid crystal display (LCD) panels, organic EL panels, and other display panels, and a chuck potential that is essentially ground potential is sufficient. Therefore, the effect of noise on measurements can be all but disregarded and the chuck and the guard structure thereof have not been given special attention, as can be seen in FIG. 8 of JP (Kokai) 2001-296547.
Nevertheless, large glass sheets have been used in most display panels in recent years in order to reduce cost and it is therefore necessary to consider the effect of these glass sheets. For instance, fifth-generation amorphous silicon processes use glass sheets that are one square meter in size or larger. Therefore, the range of motion or a region of movement of the chuck stage must be as large as three square meters. Completely enclosing and shielding a region this size has a tremendous effect on cost.
Furthermore, it is also necessary to take into consideration the effect of a larger chuck that accompanies a larger glass sheet. Floating capacity (ground capacity) C to surface area S of the chuck is represented by C=εr*(S/d), with εr serving as the material dielectric constant, when there is distance d between the chuck and ground and there is an insulator in between the chuck and ground. However, because seventh-generation panels used glass sheets that are approximately two square meters in size, they are more than twice as large as the length on one side of fifth-generation panels and floating capacity is four-times larger than that of the fifth-generation panels. Therefore, the AC impedance of the seventh-generation panels is much smaller in the high frequency than that of the fifth-generation panels. It means that it is easy to introduce noise effects for the chuck in the measurement of the seventh-generation panels. Moreover, even if the chuck has been shielded with sufficient cost by the conventional way, the measurement apparatus for testing tends to be affected by noise from various paths.
Consequently, probers and testing apparatuses for display panel testing require noise countermeasures that are different from those used for semiconductor wafers.
An object of the present invention is to provide a prober for testing display panels with which the effect of noise is reduced and a testing apparatus thereof.
Another object of the present invention is to provide a prober for testing display panels with which high-speed, high-accuracy testing is possible, and a testing apparatus thereof.
Yet another object of the present invention is to provide a prober for testing display panels and a testing method thereof with which the chuck stage is kept at high impedance in terms of alternating current (AC) signals and an electrostatic shield is effectively implemented.
Still another object of the present invention is to provide a prober for testing display panels and a testing apparatus thereof with which the effect of noise attributed to the motor drive system of the prober is reduced.
The purpose of the present invention is therefore to provide a prober for testing display panels and a testing apparatus capable of achieving these objects. This purpose is accomplished by the combination of characteristics cited in the independent claims. Moreover, the subordinate claims specify the further preferred embodiments of the present invention.